This study will investigate the binding of the pancreatic carcinogen N-methyl-N-nitrosourea (MNU) to the organelles and macromolecular constituents of the pancreatic cell in the guinea pig and will compare it to the binding of another carcinogen of the GI tract, N-methyl-N'-nitro-N-nitrosourea (MNNG). In addition, binding of these drugs to pancreatic tissue will be compared to binding to gastric and liver tissues. Emphasis will be placed on drug binding to specific sites in DNA and RNA and to specific classes of nuclear histones and acidic proteins. The dual capacity of MNU and MNNG to modify macromolecules by alkylation and carbamoylation will be stressed. Studies to detect conformational changes and structural alterations in chromatin caused by these agents will also be carried out.